Double hung window assemblies generally include a frame, an upper window sash, a lower window sash, a pair of balances, and a pair of jambliners. The jambliners are each attached to a window jamb to guide the movement of the window sashes. A seal is typically disposed between the jambliner and the window jamb to block the infiltration of air into the space between the jamb and the jambliner, and to provide a biasing force that causes the jambliners to frictionally engage the sides of the sashes to maintain the sashes at desired positions.
In conventional window assemblies, the seal typically comprises a foam backing member or a jamb-engaging flap co-extruded with the jambliner. The foam backing member typically comprises a block of polyurethane foam affixed to the jambliner by a hot-melt adhesive. Although foam backings generally provide a sufficient biasing force after installation, it has been found that the foam has a limited useful life and degrades after repeated exposure to environmental elements such as wind and rain. As a result, the foam becomes brittle and hard, losing elasticity and the ability to prevent the leakage of air and moisture. Although in such instances replacement of foam backings is necessary, replacement can be quite messy and tedious, as the hot-melt adhesive must be reapplied for attachment of a new foam backing member.
The use of co-extruded flaps has eliminated the difficulty associated with the removal and replacement of foam backings, as the jambliner and the flap are integrally formed. However, such an integral construction has led to the need for replacement of the entire jambliner when the flap is inoperative due to defective design, breakage, or wear and tear. Furthermore, the process of co-extruding such flaps is often of increased complexity due to the differential cooling rates associated with the material used to form the flap and the material used to form the remainder of the jambliner. Moreover, the compression characteristics of co-extruded members cannot be altered after fabrication.